Pitch adjustment means for track assemblies

ABSTRACT

An adjustable track assembly comprises a plurality of shoes closely coupled together by at least one articulated link assembly. Each pair of adjacent links are pivoted together by a pivot pin to define a predetermined pitch length between each adjacent pair of pivot pins. At least one of the pivot pins has eccentric cam means formed thereon for selectively adjusting the pitch length between a respective pair of adjacent pivot pins.

United States Patent 1 Boggs et al.

[ FBI). 20, 1973 [54] PITCH ADJUSTMENT MEANS FOR TRACK ASSEMBLIES [75] Inventors: Roger L. Boggs, East Peoria; Robert N. Stedman, Chillicothe, both of 111.

[73] Assignee: Caterpillar Tractor Co., Peoria, 111.

[22] Filed: Dec. 23, 1970 [21] Appl. No.: 100,852

[52] US. Cl. ..305/19, 305/54, 305/58 [51] Int. Cl. ..B60c 27/20, 862d 55/28 [58] Field of Search ..305/58, 59, 36, 42',152/187, 152/191 [56] References Cited UNITED STATES PATENTS 1,063,493 6/1913 Allen ..305/58 X 1,278,150 9/1918 Houghton ..305/59 X 3,601,212 8/1971 2,273,950 2/1942 3,032,376 5/1962 Blazek ..305/59 X Primary Examiner-Richard J. Johnson Attorney-Fryer, Tjensvold, Feix, Phillips & Lempio [5 7 ABSTRACT An adjustable track assembly comprises a plurality of shoes closely coupled together by at least one articulated link assembly. Each pair of adjacent links are pivoted together by a pivot pin to define a predetermined pitch length between each adjacent pair of pivot pins. At least one of the pivot pins has eccentric cam means formed thereon for selectively adjusting the pitch length between a respective pair of adjacent pivot pins.

15 Claims, 22 Drawing Figures PATENTED FEBZO 1975 3,717, 3 8'9 SHEET 1 0F 8 INVENTORS ROGER L. 50665 ROBERT N. STEDMAN 9-; Z 92'fl/ ATTORJEYS PATENTED H 2 I973 5,717, 389

SHEET 2 BF 8 INVENTORS ROGER L. 50665 ROBERT N STEDMAN PATENTEDFEBZOISYS INVENTORS ROGER L. 50665 ROBERT N ST EDMAN M, W4 PW +44% ATTORNEYS PATENTEDFEBZOI975 3,717. 389

SHEET 8 0F 8 ROGER L. 80665 ROBERT N. STEDMAN BY MWZQJQPZ QQ'I- ATTORN YS INVENTORS PATENTED H 20 m5 3', 7 1 7, 389

SHEET 7 BF 8 ads 309 3 32 g I E 15-]. E 33 t 373* I 3 ROGER E Rs ROBERT N. STEDMAN BY/ j W EZORNEYS PITCH ADJUSTMENT MEANS FOR TRACK ASSEMBLIES BACKGROUND OF THE INVENTION The recent advent of the cushioned track has dictated the need for adjustable track assemblies which are adapted to fit various tire sizes. The outside circumferences of large, newly manufactured earthmoving tires, for example, may be listed as having the same nominal size but will oftentimes exhibit circumferences which vary as much as three inches. In addition, such circumferences may initially increase, under certain operating conditions, and decrease due to subsequent wear. The above changes in tire circumferences may thus require adjustment of the circumventing track to compensate therefor.

SUMMARY OF THE INVENTION An object of this invention is to provide an economical and non-complex adjustable track assembly exhibiting a high degree of structural integrity and capability for being expeditiously adjusted and serviced. As will be hereinafter more fully explained, such adjustable track assembly finds particular application to cushioned tracks of the type disclosed and claimed in US. Patent Application Ser. No. 884,903, filed on Dec. 15, 1969 now U.S. Pat. No. 3,601,212 by Robert A. Peterson et al for Cushioned Track and Method for Driving Same. Such application is assigned to the assignee of this application.

The adjustable track assembly comprises a plurality of closely coupled ground engaging shoes and at least one articulated link assembly connected to the shoes to closely couple them together. The link assembly comprises pivot means connecting each pair of adjacent links together for pivotal movement about a common pivot axis thereof to define a predetermined pitch length between each pair of adjacent pivot axes. At least one of the pivot means comprises adjustment means for selectively adjusting the pitch length between a respective pair of adjacent pivot axes to thus accommodate the track assembly to various tire sizes. In the preferred embodiment, such adjustment means comprises a rotatable cam formed integrally with a pivot pin of the pivot means.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of a cushioned track embodying the pitch adjustment means of this invention in a track assembly thereof;

FIG. 2 is a sectional view taken in the direction of arrows II-ll in FIG. 1;

FIG. 3 is an enlarged, side elevational view of a portion of the track assembly employed in the FIG. I cushioned track;

FIG. 4 is a top plan view of the FIG. 3 track assembly with portions broken-away and removed for clarification purposes;

FIG. 5 is an exploded, isometric view of a pivot and pitch adjustment means employed in the FIGS. 3 and 4 track assembly;

FIGS. 6 and 7 are views similar to FIGS. 3 and 4, respectively, but illustrating a modified form of the track assembly;

FIGS. 8-10 are views similar to FIGS. 3-5, but illustrating a further modification of the track assembly;

FIG. 10a is a fragmentary and partly sectioned top elevational view illustrating a still further modification of the track assembly;

FIG. 11 is a side elevational view illustrating a locking means for locking the pitch adjustment means of this invention in place;

FIG. 12 is a partial sectional view, taken in the direction of arrows XII--XII in FIG. 1 1;

FIGS. 13 and 14 are views similar to FIGS. 11 and 12, but illustrating a modified form of the locking means;

FIGS. 15 and 16 are views similar to FIGS. 11 and 12, but illustrating a further modification of the locking means;

FIGS. 17 and 18 are views similar to FIGS. 13 and 14, but illustrating a still further modification of the locking means;

FIG. 19 is an enlarged sectional view similar to FIG. 7 but illustrating a sealing arrangement therein for sealing the pitch adjustment means of this invention; v

FIG. 20 is an enlarged sectional view similar to FIG. 9, but illustrating a modification of the sealing arrangement; and

FIG. 21 is an end elevational view of one of the eccentric cup members employed in the FIG. 20 track assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 illustrate a cushioned track 20 adapted to replace conventional tires or the like employed in standard earthmoving equipment, such as wheel-type tractors. The cushioned track comprises an annular resilient spacer means 21 having a substantially annular and polygonal-shaped endless track assembly 22 mounted completely therearound. The resilient spacer means may comprise an air-inflated rubber tire or air bag, for example, mounted on a conventional rim assembly.

Other suitable types of spacer means are disclosed in above-referenced US. Pat. Application Ser. No. 884,903. The rim may be suitably connected to a vehicles drive axle (not shown) to be driven and rotated about a central axis X thereof by an internal combustion engine (not shown). The illustrated tire spacer means embodiment may comprise suitably integrated inner liner, body plies and tread plies.

Endless track assembly 22 comprises a plurality of closely coupled ground engaging shoes 23 circumferentially surrounding the spacer means. An annular articulated link assembly or connecting means 24 is preferably positioned on each side of the spacer means and from a respective side wall thereof. The identical link assemblies may be bolted or otherwise suitably connected to radially inner surface portions of the shoes to closely couple them together.

Inner surface portions of the shoes intimately contact and compress substantially all of the periphery of the spacer means so that such periphery assumes a substantially circumferentially continuous and polygonalshaped configuration for driving purposes. Such driving relationship is fully described in above-referenced US. Pat. Application Ser. No. 884,903.

A problem encountered with such cushioned tracks is one of adapting same to tires having aried circumferences. The pitch length of the links must be selected to provide the above-mentioned intimate contact between the shoes and spacer means to afford the desired driving characteristics.

FIGS. 3 and 4 illustrate a portion of link assembly 24 as comprising adjacent pairs of identical links 25. Each pair of links are pivotally connected together for pivotal movement about a common pivot axis Y by pivot means 26. The illustrated link embodiment is of the fork and blade type comprising a fork end portion 27 positioned to receive a blade end portion 28 of the adjacent link therein.

Each link may be secured to its respective shoe 23 by means of bolts 29 and 30. Bolt 30 cooperates with a collar portion 31 slit at 32 to form a locking or clamping means. Such releasable locking means functions to retain a pivot pin 33 of the pivot means in a locked, non-rotative position in the assembly.

Pivot pin 33 is positioned substantially parallel relative to cushioned tracks central rotational axis X (FIG. 1) and substantially intermediate a respective pair of adjacent shoes connected together thereby. Such an arrangement facilitates a close coupling of the shoes together and also permits them to move into contact with the ground at the formed footprint in a substantially smooth and uninterrupted manner. In addition, the shoes are permitted to completely mask the periphery of the spacer means for protection and antidirt infiltration purposes.

It should be further noted in FIGS. 1 and 3 that first and second lugs 34 and 35 are formed integrally with each shoe at respective ends thereof. The lugs function in conjunction with the disposition of pin 33 to completely mask each other during rotation of the cushioned track. In particular, first lug 34 of one shoe will substantially underlie the covering second. lug 35 of an adjacent shoe to protect the spacer means against damage and to prevent dirt infiltration during all phases of machine operation.

Although in certain applications the outer surface portions of the track shoes may be smooth and uninterrupted, i.e., void of grousers, the majority of earthworking applications require at least one grouser 36 for increased traction and related operating purposes. The illustrated track shoes, for example, each employ three grousers disposed parallel to rotational axis X of the cushioned track and positioned to extend radially outwardly relative thereto. The grousers extend at least substantially fully across the width of the shoe and are preferably positioned with the outboard grousers closely adjacent to the pivotal connection at pin 33.

As more clearly shown in FIGS. 4 and 5, pivot pin 33 of pivot means 26 comprises rotatable and cylindrical cam means 37 having a central longitudinal axis Z. The cam means is formed on an intermediate pin portion disposed eccentrically relative to aligned and concentric, cylindrical outboard pin portions 38 and 39 which have the different diameters, in the adjusted position shown. The cam means, slip-fitted into mating bore formed in blade portion 28 of the link, is locked in a non-relative position by clamping means formed by slotted collar 31 in cooperation with bolt 30.

The outboard pin portions are pivotally mounted in bearing bushings 40 and 41, respectively, each pressfitted or otherwise suitably attached to the fork portion =27 of theadjacentlink. The outboard portions of the pin are thus mounted for pivotal movement about their common pivot axis 1 whereas intermediate cam portion 37 is centered on its axis Z which may be selectively displaced within a distance A to effect the desired pitch length adjustment between adjacent pivot axes Y Such pitch length adjustment is made by first loosening each bolt 30 and by inserting a conventional Allen head wrench into socket 42 of pin 33 (FIG. 5) to rotate the pin a predetermined amount. The number of eccentric cam means employed in a particular cushioned track application will, of course, depend upon various design parameters such as tire size, the length of each link, etc. Maximum adjustment of each pitch length, through distance A, is effected by rotating pin 33 from its position as illustrated in FIG. 3. Bolts 30 are then-retightened to lock the pin in its new, readjusted position. a

It should be noted that the step-down relationship 0 pin portions 37, 38 and 39 facilitates expeditious and precise assembly of the pivot means. In particular, as shown in FIG. 4, the rightwardly disposed surface portions of pin portions 37 and 38 are coincident, whereas theoppositely disposed outer surface portions of pin portions 37 and 39 are coincident. Thus, upon installation the pin may be readily inserted through bearing bushing 40, blade portion 28 of the one link and into bushing 41.

FIGS. 6 and 7 illustrate a modified track assembly wherein the primary change has been made to a pivot means 26a. Structures corresponding to those illustrated in FIGS. 3-5 are depicted by like numerals, but with the numerals appearing in FIGS. 6 and 7 being accompanied by an a. A like numbering procedure will be used for purposes of briefly describing the subsequent modifications and embodiments, but with the numeral employed therewith being accompanied by successive lower case letters.

The FIGS. 6 and 7 embodiment essentially differs from the FIGS. 3-5 embodiment in that a rotatable cam means 37a is pivotally mounted in a bearing bushing 40a, to pivotally connect each pair of adjacent links 250 together. Concentric outboard pin portions 380 and 39a may be slip-fitted into bores suitably formed in the fork end portion of the link. Such outboard pin portions are clamped in place by means of bolt 30a which cooperates with slotted collar portion 31a of the link for locking purposes.

The FIGS. 8-10 embodiment comprises two-part links 25b each having such parts positioned to abut each other to form fork portion 27b and blade portion 28b. Such an arrangement facilitates assembly in that a cam portion 37b of a pin 33b is first mounted in bearing busing 40b press-fitted into the blade end of one link. Each part of the fork end of the adjacent link is then slip-fitted onto a respective outboard pin portion 38b or 3912, which are coincident and identical. Bolts 29b and 30b are then suitably attached to track shoes 23b and the links to complete the assembly. As previously explained outboard pin portions 38b and 39b are clamped in place by means of bolts 30b and collar portion 31b.

FIG. 10a illustrates a modification similar to the FIGS. 8-10 track assembly wherein each link of each link assembly 240 comprises laterally spaced parts. Pivot means 260 pivotally connects first ends of a first two part link to the inwardly positioned second ends of a second, identical two part link. A pin 33c extends through an elongated bearing bushing which pivotally mounts eccentrically disposed pin portion 37c therein.

Outboard and aligned pin portions 380 and 39c are slip-fitted and locked as before into bores formed in the first ends of the first two-part link. The second ends of the second two-part link are attached to the ends of the bearing bushing to permit the adjacent links to pivot relative to each other. The relative position of longitudinal pivot axis Z of the pin and thus adjustment A is determined by the rotative position of cam portion 37c, as above described. FIGS. 11-18 illustrate various locking means embodiments which may be substituted in lieu of cooperating bolt 30 and slotted collar 31 which form the clamping means for the FIGS. 3-10a track assembly embodiments.

In FIGS. 11 and 12, a link 25d has a combined pivot pin and cam means 33d attached thereto by a plate 31d. A machine screw 30d is releasably attached to an end of the pin to selectively position the ends of the plate in diametrically opposed slots 32d formed in the link. Thus, rotation of the plate 180 from its illustrated FIG. 11 position will function to vary the pitch length between a pair of adjacent pivot axes through the distance A as explained above.

FIGS. 13 and 14 illustrate a link 25e having a combined pivot pin and cam means 33e positively locked therein by means of a set screw 30c threaded into the link. The conical end of the screw engages either one of the diametrically opposed like-shaped depressions 32e for adjustment purposes.

FIGS. 15 and 16 illustrate a link f having a combined pivot pin and cam means 33f positively held against rotation therein by means of a machine bolt f. Diametrically opposed slots 32f are formed on each side of the pin to permit the above-described selective adjustment of the pitch length between adjacent pivot axes.

FIGS. 17 and 18 illustrate a link 25g having a combined pivot pin and cam means 333 mounted therein. The pivot pin may have an enlarged head or plate 31g formed as an integral part thereof to provide the means for selectively adjusting pitch length. In particular, diametrically opposed apertures 32g are formed in such head and are adapted to alternatively receive a machine screw 30g therein which is threadably attached to the link for adjustment purposes.

If so desired, a sealing arrangement may also be employed to seal and lubricate the pivot pin in order to extend its life by retaining lubricant in the bearing area and by keeping out abrasive material.

FIG. 19 illustrates a means for sealing the fork and blade type links shown in FIGS. 6 and 7 by employing a seal of the type fully disclosed in US. Pat. No. 3,390,922, assigned the assignee of this invention. The FIG. 19 embodiment essentially differs from the FIG. 7 embodiment in that the pivot pin 33h of pivot means 26h has an enlarged head portion 38h on one end and a large cupped portion 43h suitably attached to the other end, each having annular grooves suitably disposed therein for receiving seal members 44h and 45h, respectively. Similar to the FIG. 7 embodiment, end portions 38h and 43h are eccentric to hearing portion 37h and bushing 40h to provide the cam action necessary for adjustment purposes. Each of said end portions 38h and 43h are slip-fitted into bores suitably formed in the fork end portions 27h of the links 25h and clamped in place by means previously described. The small pin portion 39h is press-fitted into a bore suitably formed in cupped portion 43 and is preferably welded at assembly to keep the parts together during the operation thereof.

FIG. 20 illustrates a means for sealing the two-part links as shown in FIGS. 8-10 and previously explained. The FIG. 20 embodiment essentially differs from the FIG. 9 embodiment in that the cam portion 371' of pin 33i is widened to accommodate seal members 44i and 451 on either end thereof. Counterbores for seals 44: and 45i are provided by the use of eccentric cup members 431', shown in FIG. 21, which are press-fitted onto outboard pin portions 38i and 39i, respectively. Suitable space is provided between the fork end portions 27 i and the blade end portions 28i of links 25i to accommodate the seals 44: and 45i and cupped members 43i and 431" In FIGS. 19 and 20'it is important that the seal-bushing phase relationship does not change when the pin is rotated for adjustment purposes in order to keep the seal running in the same path which is preferably concentric to the bushing. This prevents damage to the seal which would occur if the seal was forced to run on a path on the bushing that had been previously exposed to corrosion and abrasive materials. The same path is maintained by providing the seal with an annular groove concentric and rotatable with the cam portion of the pivot means.

What is claimed is:

1. An adjustable track assembly comprising a plurality of closely coupled ground-engaging shoes and at least one articulated link assembly having adjacent pairs of links connected to said shoes to closely couple said shoes together, said link assembly comprising pivot means connecting each pair of adjacent links together for pivotal movement about a common pivot axis thereof to define a predetermined pitch length between each pair of adjacent pivot axes,

at least one of said pivot means comprising adjustment means for selectively adjusting the pitch length between a respective pair of adjacent pivot axis, and

releasable locking means for retaining said one pivot means in a locked, non-rotative position in 'said track assembly, including a split collar portion formed on at least one of said links having a portion of said one pivot means mounted therein and means releasably attached to said one link and a respective one of said groundengaging shoes for selectively and simultaneously clamping said one pivot means in said collar por- 3. The invention of claim 2 wherein one of said link assembles is positioned adjacent to each side wall of said spacer means and extends radially inwardly toward said central axis from said shoes.

4. The invention of claim 3 wherein said pivot means comprises a pin pivotally connecting each adjacent pair of said links together. 7

5. The invention of claim 4 wherein each pin is positioned substantially parallel relative to said central axis and is further positioned substantially intermediate a pair of adjacent shoes.

6. The invention of claim 5 further comprising lug means formed on each end of each shoe to be at least substantially parallel to said central axis and positioned thereon to continuously and completely overlap a lug means of an adjacent shoe whereby the entire periphery of said spacer means is completely masked during rotation thereof.

7. The invention of claim 4 wherein said adjustment means comprises a rotatable cammeans formed on said pin.

8. The invention of claim 7 wherein each of said pins has a rotatable cam means formed thereon.

9. The invention of claim 7 wherein said pivot means comprises a pin pivotally connectingeach adjacent pair of links together and wherein said cam means is cylindrical and is eccentrically formed on said pin.

10. The invention of claim 9 wherein said pin comprises aligned and concentric, cylindrical outboard pin portions and an intermediate pin portion eccentrically disposed relative to said outboard pin portions to define said cam means thereon.

11. The invention of claim 10 wherein said intermediate pin portion is attached to a first link of said pair of links and said outboard pin portions are pivotally mounted on a second link of said pair of links.

12. The invention of claim 10 wherein each of said links has a blade portion formed at one end and a fork portion formed at the other opposite end, the blade portion of said first link being positioned in and pivoted to the fork portion of said second link by said pin.

13. The invention of claim 12 wherein one of said outboard pin portions has a different diameter than the other one of said outboard pin portions and each of said links is formed as one-piece construction.

14. The invention of claim 1 wherein said adjustment means comprises a rotatable cam means.

15. An adjustable track assembly comprising I a plurality of closely coupled groundengaging shoes and at least one articulated link assembly having adjacent pairs of links connected to said shoes to closely couplesaid shoes together, said link assembly comprising f pivot means, including a pivot pin, connecting each pair of adjacent links together for pivotal movement about a common pivot axis thereof to define a predetermined pitch length between each pair of adjacent pivot axis, and

releasable locking means for retaining at least one pivot pin in a locked, non-rotative position in said track assembly, including a split collar portion formed on at least one of said links having a portion of said one pivot pin mounted therein and means releasably attached to said one link and a respective one of said groundengaging shoes for selectively and simultaneously clamping said one pivot pin in said collar portion and said one ground-engaging shoe to said one link. 

1. An adjustable track assembly comprising a plurality of closely coupled ground-engaging shoes and at least one articulated link assembly having adjacent pairs of links connected to said shoes to closely couple said shoes together, said link assembly comprising pivot means connecting each pair of adjacent links together for pivotal movement about a common pivot axis thereof to define a predetermined pitch length between each pair of adjacent pivot axes, at least one of said pivot means comprising adjustment means for selectiVely adjusting the pitch length between a respective pair of adjacent pivot axis, and releasable locking means for retaining said one pivot means in a locked, non-rotative position in said track assembly, including a split collar portion formed on at least one of said links having a portion of said one pivot means mounted therein and means releasably attached to said one link and a respective one of said ground-engaging shoes for selectively and simultaneously clamping said one pivot means in said collar portion and said one ground-engaging shoe to said one link.
 1. An adjustable track assembly comprising a plurality of closely coupled ground-engaging shoes and at least one articulated link assembly having adjacent pairs of links connected to said shoes to closely couple said shoes together, said link assembly comprising pivot means connecting each pair of adjacent links together for pivotal movement about a common pivot axis thereof to define a predetermined pitch length between each pair of adjacent pivot axes, at least one of said pivot means comprising adjustment means for selectiVely adjusting the pitch length between a respective pair of adjacent pivot axis, and releasable locking means for retaining said one pivot means in a locked, non-rotative position in said track assembly, including a split collar portion formed on at least one of said links having a portion of said one pivot means mounted therein and means releasably attached to said one link and a respective one of said ground-engaging shoes for selectively and simultaneously clamping said one pivot means in said collar portion and said one ground-engaging shoe to said one link.
 2. The invention of claim 1 further comprising an annular resilient spacer means rotatable about a central axis thereof, said track assembly mounted completely around said spacer means for utilizing said spacer means therewith.
 3. The invention of claim 2 wherein one of said link assembles is positioned adjacent to each side wall of said spacer means and extends radially inwardly toward said central axis from said shoes.
 4. The invention of claim 3 wherein said pivot means comprises a pin pivotally connecting each adjacent pair of said links together.
 5. The invention of claim 4 wherein each pin is positioned substantially parallel relative to said central axis and is further positioned substantially intermediate a pair of adjacent shoes.
 6. The invention of claim 5 further comprising lug means formed on each end of each shoe to be at least substantially parallel to said central axis and positioned thereon to continuously and completely overlap a lug means of an adjacent shoe whereby the entire periphery of said spacer means is completely masked during rotation thereof.
 7. The invention of claim 4 wherein said adjustment means comprises a rotatable cam means formed on said pin.
 8. The invention of claim 7 wherein each of said pins has a rotatable cam means formed thereon.
 9. The invention of claim 7 wherein said pivot means comprises a pin pivotally connecting each adjacent pair of links together and wherein said cam means is cylindrical and is eccentrically formed on said pin.
 10. The invention of claim 9 wherein said pin comprises aligned and concentric, cylindrical outboard pin portions and an intermediate pin portion eccentrically disposed relative to said outboard pin portions to define said cam means thereon.
 11. The invention of claim 10 wherein said intermediate pin portion is attached to a first link of said pair of links and said outboard pin portions are pivotally mounted on a second link of said pair of links.
 12. The invention of claim 10 wherein each of said links has a blade portion formed at one end and a fork portion formed at the other opposite end, the blade portion of said first link being positioned in and pivoted to the fork portion of said second link by said pin.
 13. The invention of claim 12 wherein one of said outboard pin portions has a different diameter than the other one of said outboard pin portions and each of said links is formed as one-piece construction.
 14. The invention of claim 1 wherein said adjustment means comprises a rotatable cam means. 